Spark plug for internal combustion engines



July 30, 1940. J. c. CARTER SPARK PLUG FOR INTERNAL COMBUSTION ENGINES Filed Jan. 24, 1940 INVENTOR. J6/777 C. Carter ATTORNEY.

Patented July 30, 1940 UNITED STATES PATENT OFFICE SPARK PLUG FOR INTERNAL COMBUSTION ENGINES 6 Claims.

It is commonly known that a spark plug is a device which forms a part of the ignition system in the internal combustion engines and serves.

to ignite a mixture of air and fuel in the particular cylinder of the engine to which it is operatively connected. In practice, the spark plug is screwed into the head of the respective cylinder of the engine. This must be done in such a manner as to allow no leakage of gases from 10 the cylinder. In order to effect a seal between the head of the engine and the respective spark plug, separate gaskets were used. Such gaskets were made of soft metal; sometimes copper sheathing was used, which was turned over asbestos core, and sometimes such gaskets were made entirely of copper. It was found, however, that when a gasket made of soft material such as copper, was once compressed between the cylinder head and the respective portion of the spark plug, the resiliency of the gasket was eliminated and it could not be used again. When, therefore, it was necessary to inspect the plugs to see their condition or to remove them because of some defects, it was advisable that new gaskets 5 be used, as otherwise the seal between the spark plug and the head of the cylinder was not satisfactory.

It is the purpose of my invention to eliminate the necessity of using such gaskets and yet to provide a perfect seal between said cylinder head and the respective spark plug. To solve this problem, I have devised a new and improved spark plug, which will now be described with reference to the accompanying drawing, in

which:

Fig. 1 shows the spark plug, partly in section, in its operative position within the head of an internal combustion engine.

Fig. 2 is a fragmentary sectional view of another variety of my spark plug in its operative position within the head of an internal combustion engine.

Fig. 3 is a fragmentary sectional view of still another variety of my spark plug in its operative position within the head of an internal combustion engine.

Fig. 4 is a perspective view, partly broken off, of my improved spark plug exhibiting my inventive improvement thereon.

Similar numerals refer to throughout the several views.

The spark plug of my construction follows the construction of spark plugs now in use and is composed like many conventional spark plugs of a shell, an insulator within the shell, and two similar parts electrodes. The head of a cylinder in a conventional internal combustion engine is indicated in my drawing by numeral l0. Specifically, it represents the head of a cylinder'in an engine used in automobiles. 34 indicates a cylinder, while 35 indicates a piston therein. The spark plug, which is screwed into said head, consists of an outer shell ii, an insulator i2, in which numeral [3 indicates one of the two electrodes, forming a part of said spark plug. As in all 10 ordinary spark plugs, the lower part thereof, indicated by numeral I5, is of a smaller diameter than the upper section of said shell so that at the conjunction of the two sections a shoulder I6 is formed. Ordinarily said shoulder is en- 15 tirely flat. It is this particular shoulder that in ordinary spark plugs is intended to be seated upon the surface I! of the respective section of the head H) of the cylinder. It is between said shoulder l6 and said surface I! that compressi- 20 ble gaskets were ordinarily placed.

To eliminate the need of the gaskets, I have provided said shoulder IS with an annular sharp peaked ridge l8. The ridge is preferably triangular in cross-section, as shown in Fig. l, the 25 apex of said ridge forming a cutting edge. When the threaded lower part I 5 of the shell of the spark plug is screwed in the head of the respective cylinder, said cutting edge bites or cuts into the metal forming the surface I! of head l0 abut- 30 ting said shoulder, and although the depth of a cut in groove IS in said surface, which is so made by the cutting edge of the ridge I8, is small, it is suflicient to effect a perfect seal against the escape of gases from the interior of 35 the cylinder 34.

I wish to explain that the groove l9, shown in Fig. l of my drawing, is exaggerated in order that the relation of the parts may be shown clearer, but that in actual practice the depth of the groove may be considerably smaller than would appear from. the drawing itself. I wish to add that the effectiveness of the seal has been proven by me in a number of experiments, particularly by having plugs of my invention installed in a running internal combustion engine of an automobile and that the seal effected by the ridge in contact with the head of the respective cylinders was proved efficient and satisfactory. an

The spark plug shown in Fig. 2 is on the whole identical with the spark plug shown in Fig. 1, except that the shoulder 2|, instead of being horizontal, is formed at an angle forming a cutting ridge which bites into the surface ll of the head 05 of the engine Hi. In this case, the insulator is indicated by numeral 23. One of the electrodes of the conventional spark plug is indicated by numeral 22. 25 is the threaded lower section of the shell of the plug, while numeral 20 indicates the upper and wider portion of the shell.

The spark plug shown in Fig. 3 is also identical with the spark plug shown in Fig. 1, with this exception that there are two cutting ridges 32 on shoulder 3|. Here the insulator is indicated by numeral 28, one of the electrodes by numeral 29, the upper section of the shell by numeral 21, and the narrower and threaded section of the shell by numeral 80.

It will be seen that owing to the nature of the improvement shown by me, a spark plug may be used time and again without the necessity of any gaskets, as each time a spark plug is inserted, the cutting edge will bite little more into the metal, effecting a seal between the head of the engine and said ridge on the spark plug. It will also be seen that the nature of the invention 4 adapts itself to variations without departing from the principle and spirit of my invention, and that the novelty and usefulness of my invention lies in the use of cutting means on the spark plug, to effect a sealing contact with the head of the engine. What I, therefore, claim is as follows:

1. In a spark plug for internal combustion engines in which its outer shell forms a shoulder to abut the periphery of its seat in the engine to which it is operatively connected, an annular, integrally shaped ridge on the surface of said shoulder, adapted to cut a groove in the surface of said seat.

2. In a spark plug in which its outer shell forms a shoulder above its lower part, adapted to be screwed into the head of a cylinder in an internal combustion engine, annular cutting means on said shoulder formed integrally therewith and serving, when the spark plug has been screwed into its operative position, to cut into the surface of the head to establish a leak-proof contact therewith.

3. In a spark plug for internal combustion engines in which its outer shell forms an annular shoulder to abut the periphery of its seat in the engine to which .it is operatively connected, an integrally shaped, annular ridge substantially triangular in section, the apex of said ridge being adapted to cut a groove in the surface of the seat to establish a leak-proof connection therewith.

4. In a spark plug for internal combustion engines in which its outer shell forms an annular shoulder to abut the periphery of its seat in the engine to which it is operatively connected, a plurality of integrally shaped, annular ridges disposed concentrically with the shoulder on the face thereof, said ridges being adapted, when the spark plug has been operatively set, to out into the surface of the seat to establish a leak-proof connection therewith.

5. In a spark plug for internal combustion engines, in combination, a threaded outer shell adapted to be screwed into the head of an internal combustion engine, and an integrally formed annular cutting ridge on said shell, adapted to cut a groove in the surface of the head of the engine when the spark plug is screwed into its operative position.

6. In a spark plug for internal combustion engines, in combination, a threaded outer shell adapted to be screwed into the head of an internal combustion engine, and integrally formed annular cutting means on said shell adapted to out grooves in the surface of the head of the engine when the spark plug is screwed into its operative position, to effect a leaf-proof connection therewith.

JOHN C. CARTER. 

